Minimal differential pressure venting system

ABSTRACT

A power train assembly includes a housing having a exterior wall that defines a partition between an internal chamber and the environment. Portions of the exterior wall define a housing aperture within the exterior wall. A vent plug engages the portions of the exterior wall that define the housing aperture. Portions of the vent plug define a vent aperture that is smaller than the housing aperture.

BACKGROUND OF INVENTION

[0001] 1. Technical Field of The Invention

[0002] The present invention generally relates to a venting system for power train components. More specifically, the present invention relates to a vent plug adapted to control the pressure differential between an interior chamber of a power train component and the ambient pressure external of the power train component.

[0003] 2. Description of the Prior Art

[0004] In an automotive vehicle, power train components are vented to prevent the pressure therein from becoming too high or too low. In operation, the internal components and the lubrication oil within power train components such as the engine, transmission, transfer case, axle, or like device becomes hot. As the temperature increases, the pressure increases. If the pressure within the interior chamber of any of these power train components becomes too high, seals can be damaged. Additionally, when the pressure becomes too low, due to a thermal shock from high to low temperature, such as when the vehicle drives through water, the seals can allow water and contamination to be ingested. Therefore, it is necessary to vent these components to prevent the pressure from becoming too high or too low.

[0005] One problem with venting the interior chamber of a power train component to the environment is that internal lubrication can be vented from the interior chamber and outside contamination such as water can be ingested into the interior chamber. Many power train components have been designed with devices to prevent this. In some circumstances, power train components includes a rubber hose that is clamped to a nipple connector in fluid communication with the interior chamber. The hose extends away from the power train component to a position less likely to experience contamination, such as water. Usually a valve device is mounted at the end of the rubber hose, opposite from the nipple connector. Other devices are mounted directly onto the power train component and included complicated features to prevent oil from being vented from the interior chamber and to prevent contaminants from being ingested into the interior chamber.

[0006] As seen from the above, there is a need for an improved power train venting system that will provide venting of the interior chamber of a power train component to the environment while preventing contaminants from being ingested.

[0007] A principle object of this invention is to provide a power train venting system having a simple vent plug that will minimize the pressure differential between the internal chamber of a power train component and the environment.

[0008] It is another object of this invention to provide a power train venting system that will minimize the venting of internal lubrication to the outside environment and minimize the ingestion of contamination into the internal chamber of the power train component.

SUMMARY OF THE INVENTION

[0009] The disadvantages of the prior art are overcome by providing a power train component venting system, in accordance with the present invention, in which the power train assembly includes a housing having an exterior wall having portions that define a housing aperture. A vent plug is positioned with the housing aperture and includes portions that define a vent aperture that is smaller than the housing aperture.

[0010] In a first aspect of the present invention the exterior wall includes an exterior surface and an interior surface, and the vent aperture is positioned either outboard of the exterior surface, inboard of the interior surface, or between the exterior surface and the interior surface.

[0011] In another aspect of the present invention the vent plug defines an outwardly extending conical nozzle having a vent aperture that is positioned either outboard of the exterior surface, inboard of the interior surface, or between the exterior surface and the interior surface.

[0012] In a further aspect of the present invention the assembly includes more than one vent plug mounted thereon.

[0013] In still another aspect of the present invention the housing aperture includes an inner surface and the vent plug includes an outer surface, substantially the same shape as the inner surface of the housing aperture but smaller, such that when the vent plug is pressed into the housing aperture there is an interference fit such that the vent plug is frictionally held therein.

[0014] In yet another aspect of the present invention the vent plug includes an annular flange extending radially thereabout that is adapted to engage an outer surface of the exterior wall and provide a stop to position the vent plug within the housing aperture.

[0015] The aspects of the present invention provide a power train venting system that has a simple vent plug that minimizes the pressure differential between the internal chamber of a power train component and the environment and minimizes the venting of internal lubrication to the outside environment and the ingestion of contamination into the internal chamber of the power train component.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 is a cross sectional view of a rear axle assembly of the present invention;

[0017]FIG. 2 is an enlarged exploded view of the portion of FIG. 1 enclosed by the circle numbered 2;

[0018]FIG. 3 is an enlarged view similar to FIG. 2 wherein the vent plug has a vent aperture that is inboard of the internal surface of the external wall of the housing;

[0019]FIG. 4 is a view similar to FIG. 3 of a second preferred embodiment wherein the vent plug has a vent aperture that is outboard of the external surface of the exterior wall of the housing;

[0020]FIG. 5 is a view similar to FIG. 3 of a third preferred embodiment wherein the vent plug has a vent aperture that is between the internal surface and the external surface of the exterior wall of the housing;

[0021]FIG. 6 is view similar to FIG. 3 of a fourth preferred embodiment wherein the vent plug has a conical nozzle shape and the vent aperture is inboard of the internal surface of the external wall of the housing;

[0022]FIG. 7 is view similar to FIG. 3 of a fifth preferred embodiment wherein the vent plug has a conical nozzle shape and the vent aperture is outboard of the external surface of the external wall of the housing; and

[0023]FIG. 8 is view similar to FIG. 3 of a sixth preferred embodiment wherein the vent plug has a conical nozzle shape and the vent aperture is between the internal surface and the external surface of the exterior wall of the housing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Referring to FIG. 1 a rear axle assembly of the present invention is generally shown at 10. The rear axle assembly 10 includes a housing 12 that has an exterior wall 14. The exterior wall 14 defines a partition between an internal chamber 16 of the housing 12 and the environment 17.

[0025] As more readily seen in FIG. 2, the exterior wall 14 includes an exterior surface 30 and an interior surface 32. Portions of the exterior wall 14 define a housing aperture 18 extending through the exterior wall 14 and interconnecting the internal chamber 16 with the environment 17. The housing aperture 18 can be machined within the exterior wall 14, cast in place, or otherwise formed.

[0026] Referring to FIGS. 2 and 3, a vent plug 20 is positioned within the housing aperture 18. The vent plug 20 engages the portions of the exterior wall 14 that define the housing aperture 18. Preferably, the vent plug 20 is generally cup shaped and has a sidewall 22 with an outer surface that is shaped substantially the same as an inner surface 24 of the portions defining the housing aperture 18. However, the overall size 23 of the vent plug 20 is slightly larger than the overall size 25 of the housing aperture 18. As a result of this size differential, when the vent plug 20 is pressed into the housing aperture 18, there is an interference fit between the inner surface 24 of the housing aperture 18 and the outer surface of the sidewall 22 of the vent plug 20 such that the vent plug 20 is frictionally held, via a press fit engagement, within the housing aperture 18.

[0027] Preferably, the vent plug 20 includes an annular flange 26 extending radially from an outboard end of the outer surface of the sidewall 22 of the vent plug 20. The annular flange 26 provides a stop that engages the exterior wall 14 to control how far the vent plug 20 is inserted within the housing aperture 18.

[0028] Portions of the vent plug 20 define a vent aperture 28 extending therethrough. The vent aperture 28 is smaller than the housing aperture 18 and is preferably coaxial with the housing aperture 18.

[0029] In a first preferred embodiment, the vent plug 20 is oriented such that the cup shape of the vent plug 20 faces outward, away from the interior of the housing 12. A vent aperture 18 is positioned axially inboard of the interior surface 32, as shown in FIG. 3. Alternatively, in a second preferred embodiment, the vent plug 20 a is oriented such that the cup shape of the vent plug 20 a faces inward, toward the interior of the housing 12. The vent aperture 18 is positioned axially outboard of the exterior surface 30, as shown in FIG. 4. Finally, in a third preferred embodiment, the vent plug 20 b is oriented such that the cup shape of the vent plug 20 b faces outward, away from the interior of the housing 12, similarly to the first preferred embodiment. However, the vent plug 20 b of the third preferred embodiment is more shallow than the first preferred embodiment, such that the vent aperture 18 is positioned between the exterior surface 30 and the interior surface 32 of the exterior wall 14, as shown in FIG. 5.

[0030] In order to reduce the noise generated by air flowing through the vent aperture 18, the vent aperture 18 can be formed at a distal end of a conical nozzle that extends axially outward toward the exterior environment 17. In a fourth preferred embodiment, the vent plug 20 c includes a conical nozzle extending axially toward the exterior environment 17, wherein the distal end of the conical nozzle is positioned inboard of the interior surface 32, such that the vent aperture is positioned inboard of the interior surface, as shown in FIG. 6. Alternatively, in a fifth preferred embodiment, the vent plug 20 d includes a nozzle having a distal end positioned outboard of the exterior surface 30, such that the vent aperture 18 is positioned outboard of the exterior surface 30, as shown in FIG. 7. Finally, in a sixth preferred embodiment, the vent plug 20 e includes a nozzle having a distal end that is positioned between the exterior surface 30 and the interior surface 32, such that the vent aperture 18 is positioned between the exterior surface 30 and the interior surface 32 of the exterior wall 14, as shown in FIG. 8.

[0031] Preferably, the assembly 10 includes one vent plug 20 having one vent aperture 18, and the cross sectional area of the vent aperture 18 itself will be determined based upon the characteristics of the assembly. Generally, the cross sectional area of the vent aperture will depend upon the volume of the internal chamber 16, the heat generated by the assembly 10, and the pressure generated by the assembly 10. The size of the vent aperture 18 must be large enough to provide sufficient venting of the assembly 10, however, the vent aperture 18 must be small enough to prevent contamination from entering the internal chamber 16, as discussed below.

[0032] In operation, the vent aperture 18 will experience pressure fluctuation which will cause air to be vented bi-directionally through the vent aperture 18. Air is vented outward through the vent aperture 18 when the pressure within the internal chamber 16 is higher than the pressure outside the assembly 10. Air is ingested inward through the vent aperture 18 to the internal chamber 16 when the pressure within the internal chamber 16 is less than the pressure outside the assembly 10. In operation, the pressure constantly fluctuates as the pressure between the internal chamber 16 and the environment are equalized, hence the differential pressure venting is accomplished with minimal devices and negative interactions.

[0033] The cross sectional size of the vent aperture 18 is calibrated to minimize the pressure differential between the internal chamber 16 and the environment. By minimizing the pressure differential, the pressure fluctuations are minimized such that if some contamination, such as water, is ingested into the internal chamber 16, the volume ingested will be small enough to be boiled off under normal operating conditions. Preferably the vent aperture is round, however, the shape of the vent aperture 18 can be other shapes as appropriate for a particular application. Preferably, the area of the vent aperture 18 is on the order of 1.8 square millimeters or less.

[0034] Alternatively, the assembly 10 could include more than one vent plug 20. If more than one vent plug 20 is used, the total cross sectional area of the vent apertures 18 must be calibrated such that all of the vent apertures 18, in combination, meet the requirements mentioned above.

[0035] The foregoing discussion discloses and describes six preferred embodiments of the invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that changes and modifications can be made to the invention without departing from the scope of the invention as defined in the following claims. The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. 

What is claimed is:
 1. A power train assembly comprising: a housing having a exterior wall defining a partition between an internal chamber and the environment, portions of said exterior wall defining a housing aperture forming a passageway between said internal chamber and the environment; a power train member located within said housing; and a vent plug engaging said portions of said exterior wall that define said housing aperture, said vent plug including portions defining a vent aperture, smaller than said housing aperture, within said vent plug.
 2. The power train assembly of claim 1 wherein said vent aperture is coaxial with said housing aperture.
 3. The power train assembly of claim 1 wherein said vent aperture and said housing aperture are concurrent and coaxial within said housing.
 4. The power train assembly of claim 1 wherein said exterior wall includes an exterior surface and an interior surface, said vent aperture being positioned outboard of said exterior surface.
 5. The power train assembly of claim 1 wherein said exterior wall includes an exterior surface and an interior surface, said vent aperture being positioned inboard of said interior surface.
 6. The power train assembly of claim 1 wherein said exterior wall includes an exterior surface and an interior surface, said vent aperture being positioned between said exterior surface and said interior surface.
 7. The power train assembly of claim 1 wherein said vent plug an outwardly extending conical nozzle, said vent aperture being defined within said nozzle.
 8. The power train assembly of claim 7 wherein said exterior wall includes an exterior surface and an interior surface, said vent aperture being positioned outboard of said exterior surface.
 9. The power train assembly of claim 7 wherein said exterior wall includes an exterior surface and an interior surface, said vent aperture being positioned inboard of said interior surface.
 10. The power train assembly of claim 7 wherein said exterior wall includes an exterior surface and an interior surface, said vent aperture being positioned between said exterior surface and said interior surface.
 11. The power train assembly of claim 1 wherein said exterior wall includes portions defining at least one additional housing aperture, within said exterior wall, and an additional vent plug engaging said portions of said exterior wall that define each of said additional housing apertures, portions of each of said additional vent plug defining a vent aperture, smaller than said housing aperture.
 12. The power train assembly of claim 1 wherein said housing aperture includes an inner surface and said vent plug includes an outer surface, substantially the same shape as said inner surface of said housing aperture, said outer surface of said vent plug being sized slightly smaller than said inner surface of said housing aperture such that when said vent plug is pressed into said housing aperture there is an interference fit between said inner surface of said housing aperture and said outer surface of said vent plug such that said vent plug is frictionally held within said housing aperture.
 13. The power train assembly of claim 1 wherein said vent plug includes an annular flange extending radially from said vent plug, said annular flange being adapted to engage an outer surface of said exterior wall and provide a stop to position said vent plug within said housing aperture.
 14. The power train assembly of claim 1 wherein said vent aperture is round.
 15. The power train assembly of claim 1 wherein said vent aperture has an area that is approximately 1.8 square millimeters or less. 